Garden Pests

Vine Weevil

Many gardeners are very afraid of this root-eating plant insect, and it’s not surprising because suddenly otherwise healthy-looking plants collapse and die due to this vicious pest. It is one of the most common and devastating of all the garden pests.

Vine weevils are particularly dangerous because theirs can be a two-pronged attack as the adults eat the leaves and the grubs eat the roots. Furthermore, each adult can lay hundreds of eggs.

The vine weevil used to have a more discerning palate but nowadays they love a wide range of ornamental plants and fruits, especially those grown in containers. Adults feed mainly at night on the foliage of many herbaceous plants and shrubs. Watch out especially for your Camellias, Rhododendron, Hydrangea, Bergenia and Fuchsias.

 

How to spot

Grubs are creamy-white, have no legs, light brown heads and are up to 10mm (about 3/8in) long. You can find them curled up in a ‘C’ shape among the roots.  Often the first signs of damage from the grubs can only be spotted once a plant completely wilts and dies during autumn to spring.

Adult vine weevil can’t fly but are able to climb easily.  You’ll spot their unsightly, although not fatal damage, by semi-circular notches eaten into the edges of leaves. They are incapable of making holes in the middle of leaves, holes in the middle are more likely to have been made by Slugs and Snails.  If you spot them, put a tray down below the plant and they will fall to the ground if slightly disturbed.  But the real damage from Vine Weevils are done by the grubs which feed on the roots.

 

 

How to treat

They are difficult to control once established because of their nocturnal behaviour. Try to encourage natural predators such as birds, frogs, toads, shrews, hedgehogs, and predatory ground beetles.

Shake shrubs over an upturned umbrella.  Dislodged adults will fall into the umbrella and be easy to collect.

 

If you don't want to use pesticides in your garden, use a biological control based on Parasitic Nematodes (View our nematode product). These microscopic creatures enter the bodies of the grubs and release bacteria that will poison them. They then multiply and go on to attack other grubs.

Apply during August and early September when the soil temperature is warm enough for the nematodes to be effective (5-20 degrees C) and before the vine weevils have grown large enough to cause serious damage. After applying the biological control keep the soil moist for a fortnight after applying.

Finally, keep looking for vine weevils once you think they have been eradicated, as you don’t want to let the number of pests to build up again.


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